80 lines
2.6 KiB
C++
80 lines
2.6 KiB
C++
/*
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* Original work: Copyright (c) 2014, Oculus VR, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* RakNet License.txt file in the licenses directory of this source tree. An additional grant
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* of patent rights can be found in the RakNet Patents.txt file in the same directory.
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*
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*
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* Modified work: Copyright (c) 2017, SLikeSoft UG (haftungsbeschränkt)
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*
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* This source code was modified by SLikeSoft. Modifications are licensed under the MIT-style
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* license found in the license.txt file in the root directory of this source tree.
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*/
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/// \file DS_HuffmanEncodingTree.h
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/// \brief \b [Internal] Generates a huffman encoding tree, used for string and global compression.
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///
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#ifndef __HUFFMAN_ENCODING_TREE
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#define __HUFFMAN_ENCODING_TREE
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#include "memoryoverride.h"
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#include "DS_HuffmanEncodingTreeNode.h"
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#include "BitStream.h"
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#include "Export.h"
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#include "DS_LinkedList.h"
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namespace SLNet
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{
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/// This generates special cases of the huffman encoding tree using 8 bit keys with the additional condition that unused combinations of 8 bits are treated as a frequency of 1
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class RAK_DLL_EXPORT HuffmanEncodingTree
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{
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public:
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HuffmanEncodingTree();
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~HuffmanEncodingTree();
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/// \brief Pass an array of bytes to array and a preallocated BitStream to receive the output.
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/// \param [in] input Array of bytes to encode
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/// \param [in] sizeInBytes size of \a input
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/// \param [out] output The bitstream to write to
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void EncodeArray( unsigned char *input, size_t sizeInBytes, SLNet::BitStream * output );
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// \brief Decodes an array encoded by EncodeArray().
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unsigned DecodeArray(SLNet::BitStream * input, BitSize_t sizeInBits, size_t maxCharsToWrite, unsigned char *output );
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void DecodeArray( unsigned char *input, BitSize_t sizeInBits, SLNet::BitStream * output );
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/// \brief Given a frequency table of 256 elements, all with a frequency of 1 or more, generate the tree.
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void GenerateFromFrequencyTable( unsigned int frequencyTable[ 256 ] );
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/// \brief Free the memory used by the tree.
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void FreeMemory( void );
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private:
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/// The root node of the tree
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HuffmanEncodingTreeNode *root;
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/// Used to hold bit encoding for one character
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struct CharacterEncoding
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{
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unsigned char* encoding;
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unsigned short bitLength;
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};
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CharacterEncoding encodingTable[ 256 ];
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void InsertNodeIntoSortedList( HuffmanEncodingTreeNode * node, DataStructures::LinkedList<HuffmanEncodingTreeNode *> *huffmanEncodingTreeNodeList ) const;
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};
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} // namespace SLNet
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#endif
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